Radially outward orbital welding technique as a joining method used for inner tube to fitting connections in double wall tube configurations

Abstract

A process of welding fittings to ends of a double wall pipe comprising forming a first welded joint between an inner pipe and an inner receiver of a first fitting; forming a second welded joint between an outer pipe and an outer receiver of the first fitting; forming a third welded joint between the outer pipe and an outer receiver of a second fitting; and forming a fourth welded joint between the inner pipe and an inner receiver of the second fitting.

What is claimed is: 
     
       1. A process of welding fittings to ends of a double wall pipe comprising:
 placing an assembly of a second fitting and an inner pipe and an outer pipe into a fixture; 
 said fixture comprising: 
 a set of collets configured to retain said assembly of said second fitting and said inner pipe and said outer pipe; 
 a backing plate coupled to said set of collets, said backing plate being fluidly coupled to said second fitting; and 
 a conduit fluidly coupled to said backing plate; said conduit configured to fluidly couple a gas source to said backing plate; 
 forming a first welded joint between the inner pipe and an inner receiver of a first fitting; 
 forming a second welded joint between the outer pipe and an outer receiver of said first fitting; 
 forming a third welded joint between said outer pipe and an outer receiver of the second fitting; and 
 forming a fourth welded joint between said inner pipe and an inner receiver of said second fitting. 
 
     
     
       2. The process according to  claim 1 , wherein said fourth welded joint comprises a welded lap fillet joint or a full penetration groove welded joint. 
     
     
       3. The process according to  claim 1 , wherein said gas source comprises an inert shielding gas, further comprising:
 flowing the inert shielding gas through the conduit to a groove formed in said backing plate; 
 flowing the inert shielding gas from said groove through said second fitting into a chamber formed between said inner pipe and said outer pipe to protect said fourth welded joint. 
 
     
     
       4. The process according to  claim 1 , further comprising:
 installing said fixture within an orbital welding device; and 
 aligning a welding electrode with said inner pipe and an inner receiver of said second fitting. 
 
     
     
       5. The process according to  claim 1 , further comprising:
 clamping said assembly of said second fitting and said inner pipe and outer pipe in a biasing member formed by said set of collets and said backing plate. 
 
     
     
       6. The process according to  claim 1 , further comprising:
 sealing said fourth welded joint between said inner pipe and an inner receiver of said second fitting by using an arc energy to melt either a full or a partial thickness of the fitting with the inner pipe. 
 
     
     
       7. A welding fixture comprising:
 a set of collets configured to retain an assembly of a second fitting and an inner pipe and an outer pipe; 
 a backing plate coupled to said set of collets, said backing plate being fluidly coupled to said second fitting; and 
 a conduit fluidly coupled to said backing plate; said conduit configured to fluidly couple a gas source to said backing plate. 
 
     
     
       8. The welding fixture according to  claim 7 , further comprising:
 a groove formed in said backing plate, said groove fluidly coupled to said conduit and fluidly coupled to said second fitting. 
 
     
     
       9. The welding fixture according to  claim 7 , wherein said fixture is configured to mount into an orbital welding device. 
     
     
       10. The welding fixture according to  claim 9 , wherein said orbital welding device includes a housing supporting an orbital welding head and adaptor configured to mount a welding electrode proximate an inner diameter of a joint between said inner pipe and an inner receiver of said fitting. 
     
     
       11. The welding fixture according to  claim 10 , wherein said welding electrode is configured to form a welded lap fillet joint between said inner pipe and said inner receiver of said fitting. 
     
     
       12. The welding fixture according to  claim 11 , wherein said welding electrode is positioned relative to said inner pipe inner diameter and configured for making a radially outward weld in a gap between the inner pipe and the fitting, wherein said gap is sealed by melting either a full or a partial thickness of the fitting with the inner pipe. 
     
     
       13. A process of joining a double walled pipe with a fitting comprising:
 placing an assembly of a fitting and an inner pipe and an outer pipe into a fixture, wherein said fitting and said outer pipe have a first welded joint; 
 mounting said fixture into an orbital welding device; 
 positioning a welding electrode relative to an inner diameter of said inner pipe proximate an inner receiver of said fitting; and 
 forming a second welded joint between said inner pipe and said inner receiver. 
 
     
     
       14. The process of  claim 13 , wherein said second welded joint is formed with a radially outward weld in a gap between the inner pipe and inner receiver of the fitting. 
     
     
       15. The process of  claim 13 , wherein said second welded joint comprises a welded lap fillet joint or a full penetration groove welded joint. 
     
     
       16. The process of  claim 13 , wherein said fixture comprises:
 a set of collets configured to retain said assembly of said fitting and said inner pipe and outer pipe; 
 a backing plate coupled to said set of collets, said backing plate being fluidly coupled to said fitting; and 
 a conduit fluidly coupled to said backing plate; said conduit configured to fluidly couple a gas source to said backing plate; 
 flowing the inert shielding gas through the conduit to a groove formed in said backing plate; and 
 flowing the inert shielding gas from said groove through said fitting into a chamber formed between said inner pipe and said outer pipe to protect said second welded joint. 
 
     
     
       17. The process of  claim 13 , further comprising:
 making said second weld as a radially outward weld in a gap between the inner pipe and the inner receiver of the fitting, wherein said gap is sealed by melting either a full or a partial thickness of the inner receiver of the fitting with the inner pipe. 
 
     
     
       18. The process of  claim 13 , wherein said second weld comprises one of an orbital welding technique or a manual gas tungsten arc welding technique.